1. Field of the Invention
The present invention relates generally to the field of electronic communications, more particularly to inter-working electronic media that operate under disparate protocols, and most particularly to improving access to emergency call centers from phone services that employ networks, such as the Internet, for packet-based data transmission.
2. Description of the Prior Art
In many parts of the world, a three-digit emergency telephone number, such as 911 in the United States and Canada, can be dialed to access emergency services from any telephone connected to a Public Switched Telephone Network (PSTN). FIG. 1 illustrates a common system arrangement for a Public Safety Answering Point (PSAP) 100 for receiving emergency calls and dispatching emergency services. The PSAP 100 includes a controller 102 and a terminal 104. The controller 102, which is a phone system much like a standard Private Branch Exchange (PBX) system, is connected to both a network of selective routers 106 that direct in-coming calls to the PSAP 100, and to a database 108 that stores information associated with telephone numbers.
In operation, when a caller dials an emergency telephone number, the call is routed to the network of selective routers 106 that determines the appropriate PSAP 100 for the call. In some instances, the call may be routed between several selective routers 106 in the network before being connected to the appropriate PSAP 100. Such further routing can occur, for example, when the first selective router 106 is too busy to handle the call. The call is then routed to the controller 102 of the PSAP 100 over a voice trunk according to a telephony protocol such as Centralized Automatic Message Accounting (CAMA) or Basic Rate Interface (BRI). The controller 102 then directs the call to an available terminal 104 to be answered by a call taker.
It should be noted that each time a phone number is transmitted from one selective router 106 to another, or from a selective router 106 to the controller 102, each digit is sent in series and each digit can take upwards of 100 milliseconds in the case of a voice trunk using a CAMA protocol. Accordingly, the caller may experience a delay on the order of 15 seconds before being connected to the PSAP 100. This delay is usually accompanied by complete silence on the line, and accordingly, callers sometimes abandon their calls believing that the system is not functioning.
The controller 102 is also connected to a database 108, typically by a serial interface such as an RS-232 type of link. The database 108, which can be a location database such as an Automatic Location Identification (ALI) database, associates telephone numbers with information, such as street addresses and jurisdictional districts for police, medical, and fire response authorities. Upon receiving a call, the controller 102 queries the database 108 for any records associated with the phone number from which the call is being made. The controller 102 then forwards the records to the terminal 104 where the records are displayed to the call taker. Querying the database 108 and transmitting the record to the terminal 104 can also incur a delay of 10 to 15 seconds.
The database 108 is based on an assumption that phone numbers are associated with telephones at fixed locations. Recently, the emergence of mobile phone systems has complicated the process of directing emergency calls to the correct PSAP 100 and providing accurate records to call takers. For mobile phones, triangulation from multiple cell phone towers can often provide at least location information necessary to direct an emergency call to the correct PSAP 100. However, phone services through networks, such as the Internet, that employ packet-based data transmission present a further dilemma. A user of such a phone system may be anywhere in the world where a network connection is available. Accordingly, few network phone service providers offer an emergency telephone number service.
FIG. 1 further illustrates how some network phone service providers presently offer an emergency telephone number service. When a user dials the emergency telephone number the service provider recognizes the emergency telephone number and accesses a look-up table that correlates the user's phone number with a phone number for an administrative line into a PSAP 100. The call is then directed across a packet-based network 120 to that administrative phone number through a gateway 122 to a PSTN 124. The gateway 122 provides a conversion from a packet-based network protocol to an analog telephony protocol appropriate for the PSTN 124. The PSTN 124 then directs the call to a phone system 126 associated with the phone number of the administrative line. The phone system 126 can be, for example, a PBX system. The phone system 126 rings a phone 128 in the PSAP 100. In this way the user is connected to a phone 128 at the PSAP 100. Unfortunately, since the phone 128 is outside of the established system for receiving emergency calls, there is no assurance that the call will be answered, or if answered, will be answered by a trained emergency call taker or appropriately prioritized. Also, no facility exists to query the database 108 since the call did not come through the controller 102, and generally a callback number cannot be displayed.
Therefore, what is needed is a way to route emergency calls made through phone services that employ packet-based data transmission networks to the existing infrastructure of emergency call centers.